ICMCTF2003 Session GP: Symposium G Poster Session

Thursday, May 1, 2003 5:00 PM in Town & Country

Thursday Afternoon

Time Period ThP Sessions | Topic G Sessions | Time Periods | Topics | ICMCTF2003 Schedule

GP-1 Low Impedance Antenna Design of Internal Linearly Inductive Coupled Plasma Source for Large Area Plasma Processing
Y.J. Lee, K.N. Kim (Sungkyunkwan University, South Korea); S.E. Park, J.K. Lee (POSTEC, South Korea); G.Y. Yeom (Sungkyunkwan University, South Korea)
In order to achieve the performance required for high resolution flat panel display (FPD) devices, especially for TFT-LCD of next generation, improved dry etch processes currently indispensable technology for semiconductor industry are required for volume manufacturing and superior critical dimension control. The plasma sources developed to date for the production of high-density and large-area plasmas mainly focused on the external spiral-type ICP sources. However, due to its large inductance with the scale-up to larger areas and the cost and the thickness of its dielectric material, the conventional ICP source using an external spiral antenna may have reached its limit in extending the process area. Therefore, in this study, a large-area plasma source with linear internal inductive antennas have been investigated as a possible candidate for the efficient and large area high-density plasma source. To minimize the inherently electrostatic coupling effect in the internal linear inductive antenna configurations, multiple-cusp magnetic fields employing permanent magnets were used and the effects of various magnet combinations and process conditions on the plasma characteristics were studied in a square shaped (830mm*1,020mm) plasma chamber. By using the magnetic fields, RF coil voltages induced on the antenna were decreased. Also, the application of the magnetic field changed the inductance value significantly depending on the arrangements of the permanent magnets. The application of the optimized magnetic field increased ion density about two times, however, the plasma uniformity was slightly decreased even though the uniformity was maintained within 10%.
GP-2 Effect of Various Plasma Treatments on the Outgassing Characteristics of MgO Layer Used for Plasma Display Panel
H.K. Hwang, B.K Song, Y.J. Lee, C.H. Yi, C.H. Jeong, G.Y. Yeom (Sungkyunkwan University, South Korea)
MgO thin film has been widely used as the surface protective layer of the plasma display panel (PDP) because of its physical stability and high secondary electron emission coefficient. However, impurities such as, H@sub 2@O, CO@sub 2@, N@sub 2@, O@sub 2@, and H@sub 2@ adsorbed on MgO layer and emitted during the operation of PDP may deteriorate the characteristics of PDP and reduce the operation lifetime. In this study, the effects of various plasma treatments on the outgassing characteristics of MgO layer were investigated. To characterize the effects of plasma treatments to MgO layer in addition to the outgassing characteristics, the change of surface roughness and surface impurities of MgO layer were also investigated using atomic force microscopy(AFM) and x-ray photoelectron spectroscopy(XPS). To study the outgassing characteristics, the MgO layer were heated up to 400°c and the outgassing species were measured as a function of temperature using a quadrupole mass spectrometer(QMS). As the plasma treatments, various plasma tools such as an atmospheric plasma system and an inductively coupled plasma(ICP) system have been used. For the atmospheric pressure plasma treatment, mixtures of He/O@sub 2@/Ar/N@sub 2@ were used at atmospheric pressure and. for the ICP treatment, Ar/O@sub 2@ gas mixtures were used at a few mTorr of pressure. We found that the plasma treatments using the atmospheric plasma system and the ICP system removed the contamination on the surface of MgO layer and also showed the increase of secondary electron emission coefficient(SEEC). Also, we found that the use of atmospheric plasma system is more effective in the plasma treatment of MgO layer of PDP due to the various benefits such as easier installation, higher throughput, lower equipment cost, etc.
GP-3 SiO@sub2@ Etching in Linearly Extended Inductively Coupled Plasmas
K.N. Kim, Y.J. Lee, B.K Song (Sungkyunkwan University, South Korea)
The development of large-area and/or large-volume plasma source with high density is desired for a variety of plasma processes from microelectronics fabrication processes to flat panel display device fabrication processes. The plasma sources developed to date for the production of high-density and large-area plasmas mainly are focused on the externally planar ICP. However, there are some problems when the external spiral antenna is scaled up to larger area plasma source. However, by inserting an antenna into plasma, the induction of a strong electric field in the plasma and the efficient transmissions of power to plasma is possible and it can be used as a large area plasma source. In this study, to improve both the plasma density and the uniformity of the internal ICP source, several internal-type linear antenna designs working with permanent magnets were used in a square shaped (830mm*1020mm) plasma chamber and the characteristics of the plasmas and SiO@sub2@ etch characteristics were investigated. The characteristics of the plasmas were measured using a quadrupole mass spectrometer and a Langmuir probe located on the sidewall of the chamber. The results showed a strong relationship between the combination of the magnets and plasma characteristics such as density and uniformity. Under optimized arrangement of the permanent magnets, the uniformity of the Ar@super+@ ion density less than 10% could be obtained while maintaining high plasma densities on the order of 1*10@super11@cm@super-3@. The etch uniformities of SiO@sub2@ etched using C@sub4@F@sub8@(NF@sub3@)/He/O@sub2@ gas mixtures showed the similar trend as that of Ar@super+@ ion density. Comparison of SiO@sub2@ etching characteristics in the linearly extended ICP with/ without the magnetic fields was also made.
GP-4 Fabrication and Characterization of Piezoelectric Self-Patternable PZT Films and their Application to Micro-Detecting System
J.S. Hwang, W.S. Kim, H.H. Park (Yonsei University, South Korea); T.S. Kim (Korea Institute of Science and Technology, South Korea)
Thick self-patternable lead zirconium titanate (PbZr@sub x@Ti@sub 1-x@O@sub 3@; PZT, x=0.52) films using photosensitive stock solution were prepared with well-developed physical and electrical properties by sol-gel method. This photoresist-free PZT solution included diethanolamine as a stabilizer, ortho-nitrobenzaldehyde(NBAL) as a cross-linking agent, and ethanol as a solvent. For the development of film pattern, a wet chemical etching after UV-exposure through pattern-mask was adopted to avoid the degradation of film possibly happened during dry etching. For applying piezoelectric self-patternable PZT film to micro-mechanical detecting system, we obtained applicable thick PZT films by controlling PZT sol concentration and manufacturing process. In this study, piezoelectric property of self-patternable films under various conditions was investigated for applying to micro-detector in bio micro-electromechanical system (bio MEMS). Electric properties such as piezoelectric coefficient, dielectric constant, and leakage current were determined. The piezoelectric coefficient is one of the most important parameter in development of MEMS incorporating piezoelectric films. The surface morphology and thickness of films were observed using scanning electron microscopy and the crystal orientation of films was determined by X-ray diffraction. Their ferroelectric and piezoelectric properties, and fatigue behaviors were measured and discussed in the point of view of applying to micro-detecting system.
GP-5 Continuous In-site-EDXRF-analysis of Coatings in a Vacuum Coating Plant
H. Esche, J. Piltz (amtec Analysenmesstechnik GmbH, Germany)
For the continuous and non destroying measurement of thickness and/or the stoichiometry of coatings a special EDXRF analyzing system was installed at the MAXIM (Institute FEP, Germany) vacumm coating plant. The EDXRF measuring head was placed inside of one of the vaccum chambers behind the coating chamber. A computer-controlled step-motor allows the positioning of the measuring head over the whole width. Thus it is possible to measure coating profiles transverse to the transport direction of the coated base material. Inside of the vacuum-sealed measuring head there are two different X-ray sources and the fluorescence radiation detector. One of the two sources operates on lower voltage and lower excitation angle using X-ray optics for an effective measurement of light metal coatings (Al,Si,Mg) down to 50 nm. The high-resolution drift camber detector is peltier-cooled and works with pulse rates of up to 50.000 cps. The water-cooled case of the measuring head allows measurements of hot coatings up to 500@super o@C/932@super o@F. The posters reports on m,easuring results from various experimental coatings.
GP-6 Modification of Wear Behaviors of High-chromium Cast Iron Alloy by N and Ti Ion Implantation
L.R. Shen, K. Wang, J. Tie, H.H. Tong, Q.C. Chen (Southwestern Institute of Physics, China); D.L. Tang, K.Y. Fu, P.K. Chu (City University of Hong Kong)
This study investigates the effects of single and dual-element (N and Ti) ion implantation on the wear and friction properties of high chromium cast iron alloys. The surface microhardness, abraded quantity, friction coefficient and microstructure are assessed by microharness measurement, abrasion machines, pin-on-disk tester, and XRD. The results show that high microhardness (>HV1300) and low friction coefficient can be achieved after N and Ti ion implantation. New CrN chemical structure is detected on the surface of alloys. The surface modification mechanisms of high chromium cast iron by ion implantation will be discussed. The process developed in this work is being applied to the surface modification of slurry pump in industrial production. The lifetime of slurry pump cylinder bores after ion implantation can be improved by more than a factor of two.
GP-7 Durable IrO@sub 2@-Ta@sub 2@O@sub 5@ Coated Ti Anodes with Surface Modified Ti Substrate by Micro-roughness and Oxygen Diffusion Layer
P.-Y. Lim (National Tsing Hua University, Taiwan, ROC); L.-C. Kuo (Industrial Technology Research Institute, Taiwan, ROC); K.L. Chang, Han. C. Shih (National Tsing Hua University, Taiwan, ROC)
The durability of the IrO@sub 2@-Ta@sub 2@O@sub 5@-coated Ti anode is one of the major concerns for its industrial applications. It is known that the early failure of the anode was usually due to the loss of the active coating layer. In this study, surface modification by the intensive micro-roughness and a thin oxygen diffusion layer on the a-Ti surface shown a significant improvement of its durability. The commercial pure grade 1 titanium was used and treated with various processes including phase transformation, thermal oxidation and chemical etching. The surface morphology and phase structure properties of the substrates were characterized by scanning electron microscopy and Auger electron spectroscopy. Subsequently, Ir-Ta precursor solution was coated on the substrate surface and forming an IrO@sub 2@-Ta@sub 2@O@sub 5@ active layer by the thermal decomposition. The durability of the IrO@sub 2@-Ta@sub 2@O@sub 5@ coated Ti anodes, with different substrate surface conditions, was examined and compared under continuous oxygen evolution reaction in H@sub 2@SO@sub 4@ acid solution.
GP-10 In-vitro Studies of the Oseo-integration in Amorphous Carbon Films.
S.E. Rodil (Instituto de Investigaciones en Materiales, Mexico); R. Olivares, H. Arzate, S. Muhl (Universidad Nacional Autonoma de Mexico)
Films of amorphous carbon (a-C) and amorphous carbon nitride (a-CN) were deposited on stainless steel substrates (AISI 316L) using a dc magnetron sputtering system. In-vitro studies were carried out on the coated samples using human osteoblasts cell culture lines. Preliminary bio-activity of carbon films to promote bone growth was assessed by cellular adhesion and proliferation, as determined by a cellular count spectroscopic technique using a well defined standard curve. Osteoblasts cells were also grown on uncoated steel and Ti coated steel samples for comparison. The degree of osteoblasts adhesion measured at 24 hrs attained maximum values for a-C films. Similarly, cellular proliferation evaluated at three, five and seven days showed an outstanding increase of osteoblasts cells for a-C and Ti coatings in contrast with uncoated steel. Oseo-integration or bone growth was evaluated by measuring the elemental composition and the substrate coverage of the mineral grown on the substrates after periods up to 21 days. Elemental composition analyses were performed by X-ray energy dispersion analysis (EDX) in a scanning microscope and X-ray photoelectron (XPS) and Auger spectroscopy. The relation between film properties (bonding, gap and composition) and cellular response is also discussed.
GP-11 Surface Characterization and Blood Compatibility of Poly(ethylene terephthalate) Modified by Plasma Surface Grafting 1
J. Wang (City University of Hong Kong); C. Pan, N. Huang, H. Sun, P. Yang, Y.X. Leng, J. Chan, G. Wan (Southwest Jiaotong University, PR China); P.K. Chu (City University of Hong Kong)
Poly (ethlene terephthalate) (PET) films as material of artificial heart valve sewing ring were treated by argon plasma discharge and grafted by different molecular water-soluble polymer-polyethylene glycol (PEG). The surface property was characterized by means of contact angle measurement, X ray photoelectron spectroscopy (XPS) and attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR). The contact angle of water decreased from the original 83.5 to 38.7. The interfacial energy also decreased from 30.66mN/m to 6.28mN/m. The ratio of oxygen to carbon increased from 0.15 to 0.25. The peak of C-O was intensified by surface modification of PET. All results revealed that PEG chains were successfully grafted on surface of PET films. The interaction between the surface-modified PETs and blood components was investigated to evaluate the blood compatibility of the samples. Activated partial thromboplastin time (APTT) of the PET-PEG was significantly longer than that of untreated PET. The observation of scanning electron microscopy (SEM) and optical microscopy indicated that the numbers of adhered, aggregated and morphologically changed platelets were significantly reduced by grafting PEG chains onto PET films. Moreover, the blood compatibility tests in vitro suggested that the blood compatibility of PET grafted with PEG was relative to molecular weight of PEG. The best blood compatibility of modified PET can be achieved as the grafted molecular weight of PEG is 6000 in this process. The mechanisms of haemocompatibility improvement were explained by hypotheses of the low interfacial free energy, the sterically hindered effect of PEG chains and the maintaining normal conformation. @paragraph@@super 1@This work was financially supported by China Key Basic research # G 1999064706, China High Tech Project 102-12-09-1, NSFC50203011 and Southwest Jiaotong University Foundation 2002B02 .
GP-12 Atmospheric Pressure Microwave CVD for Barrier Layers on Steel Sheets - Characterisation of Layer Properties
V. Hopfe, R. Liske, B. Leupolt, B. Schöneich, D. Rogler, W. Grählert (Fraunhofer Institute Material and Beam Technology Dresden, Germany); B. Schuhmacher, C. Piehl (ThyssenKrupp Stahl AG / Dortmunder OberflächenCentrum, Germany)
With the objective of developing cost effective technologies for wide area coating on temperature sensitive substrates, a range of activation methods for atmospheric pressure CVD is under assessment. Among them is a microwave remote plasma CVD method which can be applied for continuous deposition of oxide layers on moving steel sheet substrates. High deposition rates for e.g. silica coatings could be achieved being typically in the order of 20 - 80 nm/s. Structure and chemical composition of the coatings, as well as thickness and homogeneity of the layers were characterised by UV-VIS-NIR spectroscopic ellipsometry, mid-IR FTIR reflectance spectroscopy, XPS, GDOS, FE-SEM, and AFM. The optical functions of oxide layers were derived from wideband ellipsometric measurements and infrared reflectance data by optical modelling. Furthermore, the corrosion behaviour of the coatings were characterised by electrochemical methods (Scanning Kelvin Probe, cyclovoltammetry), and weathering tests. FTIR spectra of the silica layers exhibit the typical phonon bands of an amorphous SiO@sub 2@ network. The layers contain changing amounts of - OH groups, but no organic residues were detected. The layers exhibit a complicated internal microstructure with a changing porosity from the substrate / layer interface to the surface which can be sufficiently described by a gradient layer optical model based on an effective media approximation. FE-SEM images and cyclovoltammetric measurements show that the CVD coatings cover well the subjacent zinc layer. According to first results of weathering tests the corrosion resistance is promising in comparison to conventional pretreatments. The results of layer characterisation will be used to set-up a data base for application oriented coating selection as well as for technology evaluation.
GP-13 Hard Lubricating Coatings for Cutting Tools
N.M. Renevier, G. Dyson, S. Taylor, S. Yang, D.G. Teer (Teer Coatings Ltd, United Kingdom)
Two coatings based on Graphite (Graphit-iC@super TC@) and MoS2 (MoST@super TM@) have been extensively studied for their excellent tribological properties [1], they combine low friction with high hardness, high load bearing capacity and exceptionally low wear. Both coatings act as solid lubricants providing protection for both the coated surface and any opposing uncoated surface. Today both coatings are used in large scale production in a wide range of manufacturing processes ( e.g. forming and cutting applications) [2, 3]. The benefits of those coatings are both ecological and economical. The economical benefits can be obtained from the elimination of the direct costs of lubricants, from longer tool life and less tool maintenance, from improved quality of machined parts as well as from the indirect costs of parts cleaning and waste disposal. Enhanced performances have been obtained with both coatings when machining difficult materials such as high alloyed steels. Those results have been taken from various machining processes, which include tapping as well as drilling and milling operations. The industrial results are correlated with a comprehensive analysis of the tools and the workpiece material.@paragraph@[1] V. Fox, A. Jones, N.M. Renevier, D.G. Teer, Surface and Coatings Technology 125 (2000)347.@paragraph@[2] N.M. Renevier, H. Oosterling, U. Koenig, H. Dautzenberg, B.J. Kim, L. Geppert, F. G.M. Koopmans, J. Leopold, presented at ICMCTF 2002, San Diego, Ca, USA, April 22-26, in print in Surf. Coat. Technol.@paragraph@[3] N.M. Renevier, D.G. Teer, ITC 2002 on tool steel, Karlstad, Sweden Conference proceeding.
GP-14 Corrosion-fatigue Behavior of a 316L Stainless Steel Coated with Different under Stoichiometric TiNx Deposits
J. Berrios-Ortiz (Universidad Central de Venezuela); D.G. Teer (Teer Coatings Ltd, United Kingdom); E.S. Puchi-Cabrera (Universidad Central de Venezuela)
The effect of three different TiNx deposits on the corrosion-fatigue behavior of a 316L stainless steel has been investigated. Standard tensile and fatigue samples of the substrate material were coated industrially by close field unbalanced magnetron sputtering (PVD) at Teer Coatings Ltd. Hartlebury, U. K., with TiN0.55, TiN0.65 and TiN0.75 deposits of approximately 3 microns in thickness. The samples were subsequently tested under rotating bending conditions at a frequency of 50 Hz employing a solution of 3 wt.% NaCl, in order to determine the fatigue strength of both the coated and uncoated substrate. The fatigue fracture surfaces of the coated samples were analyzed by means of scanning electron microscopy (SEM) and EDS techniques in order to determine the crack initiation sites and to study the cracks propagation throughout the transverse and longitudinal sections of the samples. It has been determined that the application of such coatings to the steel substrate gives rise to a significant increase in the fatigue life under corrosion conditions, in comparison with the uncoated substrate. From the microscopic point of view it has been observed that the deposit applied remains well adhered to the substrate during testing. Also, it has been determined that the fatigue cracks originate from the surface of the coatings, rather than from the substrate-deposit interface. It has been concluded that the increase in corrosion-fatigue properties of the coated substrate is associated with the apparent good adhesion of the deposits and their excellent corrosion resistance.
GP-15 Performance Comparison between Ti-Al-N and Ti-Al-Si-N Coated Tools for High Speed Machining
M.C. Kang, J.S. Kim, K.H. Kim (Pusan National University, South Korea)
The technique of high speed machining is widely studied in machining fields, because the high efficiency and accuracy in machining can be obtained. Concerning to cutting tool that is coated by hardened material such as TiC, TiN, TiAlN, the severe tool damage in machining high-hardened like SKD series material becomes hot issue. Titanium nitride films have been widely applied to coatings, bearings, and forming tools because of their high hardness and low coefficient of friction. Recently, quarternary materials system of Ti-Al-Si-N was exploited for their mechanical and oxidation properties, and showed better properties than those of Ti-Al-N or Ti-Si-N coating layers. These reports are, however still to evaluate the performance of tools when the quarternary coating layer is applied to. In this work, Ti-Al-N and Ti-Al-Si-N coatings were deposited on WC-Co substrates by cathodic arc ion plating(AIP) method. Micro-hardness measurement was conducted by means of Knoop micro-hardness indentor. The Ti-Al-Si-N film had higher hardness than Ti-Al-N film. Incorporation of a small amount of Si into Ti-Al-N had large effect on the improvement in micro-hardness of Ti-Al-N film. Cutting tests of the coated tools were carried out, and their performances in high speed cutting conditions were comparatively studied between Ti-Al-N coated and Ti-Al-Si-N coated ones. Also, In order to verify tool wear distribution, normal distribution and log normal distribution by Chi squared test was considered. As the result, the newly developed Ti-Al-Si-N coated tools showed good tool life as compared with the Ti-Al-N coated tool under high speed machining condition.
GP-16 Quality Evaluation of Coating Tool by Measurement of Edge Roughness
M.C. Kang, J.S. Kim, K.H. Kim (Pusan National University, South Korea)
TiN-based coating tools show an unique wear mechanism especially at cutting the hardened steel. Among cutting tools, end-mill is an essential tool to generate complex surface in die & mold and precision parts, and it has been developed with various materials and tool shapes. The most important factor to evaluate the performance of coating end-mill is still the wear characteristics of flank face. In addition to the flank wear, the tool edge roughness generated by the chipping is another important factor in aspects of material property and machinability evaluation, and it affects the quality of machined surface. Up to now, there is no direct method for measurement of tool edge roughness. In this study, the edge roughness of coating end-mill is indirectly measured along the axial direction of workpiece. The theoretical equation is derived in consideration of tool geometry. Finally, the optimal conditions to measure the tool edge roughness by the proposed method are presented through the theoretical review and experimental identification.
GP-17 Determination of Energy Flows in a Tapping Operation
F. Jolliet, E. Bergmann (Geneva School of Engineering, Switzerland); T. Cselle, M. Morstein (Platit AG, Switzerland); S. Lux, B. von Zeppelin (Fraisa Ag, Switzerland)
The energy flow in a tapping operation was studied. We determined the power flowing into the workpiece and the tool and compared it with the total power input. The power flows were determined from thermocouple measurements. Various coatings were compared with respect to their influence on this power distribution.
GP-18 Investigation into the Thermal Behavior of TiBN and TiBN/TiN Coatings in Milling H13 Steel
J Hua, P. Mittal, R. Shivpuri (The Ohio State University); A. Srivastava (TechSolve); S.J. Dixit, R.S. Bhattacharya (UES, Inc.)
Coated carbide and ceramic cutting tools have significantly increased tool lives in conventional machining of ferrous and non-ferrous metals. However, in high speed machining of titanium alloys, hypereutectic aluminum-silicon alloys and hardened steel, the tool lives of coated tools are of the order of few minutes. This leads to loss of productivity due to tool changes and/or the use of low depths of cut, feeds or cutting speeds, which leads to a host of other problems. The failure of coatings to machine these hard-to-machine workpiece materials has primarily been attributed to crater and attrition wear. This in turn could be attributed to insufficient hardness, toughness and poor adhesion properties of the coatings as well as the excessive high temperatures at workpiece-tool interface. In this paper, the FEM model of TiBN and TiBN/TiN coated cutting tool in milling of H13 steel is developed. Process variables such as, temperature, pressure, stress and strain in the coating layer are analyzed during the cutting process in connection with the tool wear. The efficacy of the present FEM analysis is verified by conducting controlled milling experiments on AISI H-13 to collect the relevant tool life and force data.
GP-19 Low Temperature Deposition of CrAlN Coatings for the Application on Machine Parts
E. Lugscheider, K. Bobzin, M. Maes (Materials Science Institute, Aachen University, Germany)
PVD coated tools are nowadays state of the art in tool engineering. However the field of coating applications on machine parts was avoided for a long period of time. Main problems of PVD application on machine parts(ball bearings, gear wheels) is caused by the low annealing temperatures of 100Cr6 or 16MnCr@sub 5@ which are commonly used steels. Typical maximum deposition temperatures for these parts are in the range of about 200@super o@C, to avoid annealing. Development of a PVD process at these low temperature ranges remains difficult. A reduction of power at the cathodes as well as the etching power at the substrate subsequently leads to a decrease in hardness and adhesive strength. The reduced power at the cathodes leads to a decrease in ionization rate, which results in a drop in hardness and a reduced adhesive strength. However, new developments in PVD power supplies enable, due to bipolar pulsing, high ionization rates at low average power rates. Objective of this work is the development of a low temperature deposition pulse process, which provides hard coatings with good adhesive strengths. After deposition these coatings were then characterized to show the affect of deposition parameters on the hardness and adhesive strength of these coatings.
GP-20 On the Fatigue Behavior of a 316L Stainless Steel Coated with a PVD TiN Deposit
E.S. Puchi-Cabrera, F. Matinez, I. Herrera, J. Berrios-Ortiz (Universidad Central de Venezuela); S.J. Dixit (UES, Inc.); D. Bhat (University of Arkansas)
The effect of a TiN film on the fatigue properties of a 316L stainless steel has been investigated. Such a film was of approximately 1-3 microns in thickness and was deposited industrially by means of filtered cathodic arc. It has been determined that the application of such a coating to the steel substrate gives rise to a significant increase in both fatigue life and fatigue limit, in comparison with the uncoated steel. The increase in fatigue life have been quantified in terms of the computed values of the Basquin parameters of the different materials tested. Thus, it has been shown that, depending on the alternating stress applied to the material, the fatigue life of the steel can be increase between 400-2119%, whereas the fatigue limit was observed to increase in 22%, that is to say, 60 MPa above the fatigue limit of the uncoated substrate. From the microscopic point of view, it has been observed that the film remains well adhered to the substrate both in tension and during fatigue testing at low alternating stresses (480 MPa). However, during fatigue testing at elevated stresses (510 MPa) the coating was observed to delaminate from the substrate. Also, it has been determined that the fatigue fracture of the substrate-coating composite is dominated by the fracture of the TiN film since fatigue cracks have been observed to form first at the surface of the coating and subsequently to propagate towards the substrate. It has been concluded that the increase in fatigue properties of the coated substrate is associated mainly with the elevated compressive residual stresses present in the coating and to the apparent good adhesion of the film to the substrate observed in most of the alternating stress range explored in this work.
GP-21 Influence of an Electroless Ni-P Deposit on the Fatigue Behavior of a 7075-T6 Aluminum Alloy
A. Prieto, A. Rodriguez, M.J. Ortiz-Mancilla, C. Villalobos-Gutierrez, E.S. Puchi-Cabrera (Universidad Central de Venezuela)
The influence of an electroless Ni-P (EN) deposit on the fatigue behavior of a 7075-T6 aluminum alloy has been investigated by testing the uncoated and coated specimens under rotating bending conditions in a wide range of alternating stresses. The deposit had a mean thickness of approximately 37 microns and a high phosphorous content, above 12 wt%. Prior to fatigue testing, the static mechanical properties of the material in both conditions were also evaluated by means of tensile testing. The results of such tests indicated that fatigue testing should be conducted in the range of alternating stresses of 269-430 MPa, which corresponded to 49-79% of the yield stress of the uncoated substrate. It has been determined that the presence of the EN deposit gives rise to an increase in the fatigue life of the alloy which can achieve up to 105%, depending on the alternating stress applied to the material, in comparison with the uncoated substrate. The SEM analysis conducted on the fracture surfaces of some selected samples indicated that the fatigue failures were mainly due to the propagation of a single crack and that most of such cracks were associated with the presence of large nodules produced during the deposition process.
GP-22 Enhancement of the Ferroelectric Properties of Bi@sub 3.25@La@sub 0.75@Ti@sub 3@O@sub 12@ Thin Films under Different Annealing Processing by Metalorganic Decomposition
C.I. Kim, K.T. Kim (Chungang University, South Korea); T.H. Kim (Yeojoo Institute Technology, South Korea)
The dependence of crystallization and ferroelectric properties are related to the annealing process in Bi@sub 3.25@La @sub 0.75@Ti@sub 3@O@sub 12@ (BLT) thin films. We have systematically investigated the variation of grain sizes depending on the process condition. A two-step process to grow BLT thin films was adopted and verified to be useful to enlarge the grain size of the film and to enhance ferroelectric properties. The structure and morphology of the films were analyzed by x-ray diffraction, atomic force microscope, and scanning electron microscope. The compositional depth profile of the interfaces between the BLT thin films and electrode materials were examined using Auger Electron Spectroscopy. The BLT thin films with various annealing process were enhanced the remanent polarization, fatigue characteristics, and leakage current properties.
GP-23 Electrical Conduction Behaviors of Bi@sub 3.25@La@sub 0.75@Ti@sub 3@O@sub 12@ Thin FIlms using Pt Electrodes Prepared by a Metalorganic Decomposition Method
C.I. Kim, K.T. Kim (Chungang University, South Korea); C.I. Lee (Ansan College of Technology, South Korea)
We investigated the conduction mechanisms of the BLT films with the thickness raging from 100 to 200 nm. We have fabricated Bi @sub 3.25@La @sub 0.75@Ti@sub 3@O@sub 12@ (BLT) thin films on the Pt/Ti/SiO@sub 2@/Si substrates using a Metalorganic decomposition method. The electrical conduction behaviors of BLT thin films on Pt electrodes were analyzed based on a fully depleted film, Schottky emission, and space charge limited conduction model in the low and high electric field regions, respectively. The slope larger than 1.5 from the log I -V plot in the high-field region implies that the energy level of electron traps is continuously distributed in the energy band gap. The conduction and dielectric properties of BLT thin film depended on the film thickness and grain size. Schottky emission behavior was observed at test temperature over 100@super o@C, and the space charge limited conduction behavior appeared below the that temperature.
GP-24 Effect of Alkaly Treatment on Surface Structure and Texture of Titanium Alloy and Stainless Steel and on Calcium Phosphate Formation by the Biomimetic Method
R.L.P. Teixeira, G.C.D. Godoy, M.M. Pereira (Federal University of Minas Gerais, Brazil)
Alternatives to the plasma spraying method have been developed to obtain calcium phosphate coatings, like the biomimetic method. This process is a physicochemical method in which a substrate is soaked in a solution that simulates the physiological conditions, for a period of time enough to form a desirable layer of the calcium phosphate on the substrate. The titanium substrate usually investigated in the literature is subjected to an alkali treatment to induce the calcium phosphate formation and improve adhesion of the coating. The goals of this work are to compare the tribological effect of alkaline treatments on the surface structure and texture of two substrates titanium alloy and stainless steel, usually used for implants and orthopedic prostheses. The metallic substrates were treated with NaOH 5N at 60@super o@C for 24 hours and NaOH 20N at 90@super o@C for 30 minutes. The samples were characterized using optical microscopy, perfilometry, infrared and X-Ray diffraction spectroscopy and scanning electron microscopy. The alkaline treatment modified the characteristics of both substrates and allowed the nucleation of a calcium phosphate film. The best attacks were on titanium alloy in NaOH 5N and on stainless steel in NaOH 20N due their rougher surfaces more appropriate to form a biomimetical film.
GP-25 A Study on the Surface Anodization of Mg Alloy by Plasma Generation in Liquid Phase
Y.J. Lee, S.H. Ahn, J.G. Kim, J.G. Han (SungKyunKwan University, South Korea); R. Itatani (Daigo Ohtakacho, Japan); K.J. Yang (Dae Dong Metal Finishing Co., South Korea)
Magnesium and its alloys are known to have the smallest density among the practical metals, and to have strength properties comparable to aluminum some ferrous materials. Thus, they used as engineering materials when light-weight and high strength are necessary.@paragraph@ Because of its poor mechanical properties and corrosion resistance, magnesium was used mainly as a non-structural materials in the past. So, process together with surface modification techniques including ion implantation and annealing have solved the corrosion problem of magnesium and its alloys to some extent. But their corrosion protection is still limited because of their inherent high chemical reactivity. Therefore proper surface treatments are required further to produce protective films, which play an essential role in the corrosion protection of magnesium and its alloys.@paragraph@ In this study, anodized magnesium film was synthesized on magnesium alloy(AZ31) by anodizing for corrosion resistance and isolating character.@paragraph@ We have characterized using X-ray diffraction(XRD), second electron microscopy(SEM) to obtain information on the coated surface. Mechanical properties of anodized film were evaluated by Nano indentor. The corrosion characteristics of anodized films were first investigated by a potentiodynamic polarization test and next by electrochemical impedance spectroscopy(EIS) in a 0.32g NaCl (1 liter).
Time Period ThP Sessions | Topic G Sessions | Time Periods | Topics | ICMCTF2003 Schedule